Date: Mon, 06 Apr 1998 17:44:27 +0200 From: "Stefan Bethke" <stefan@promo.de> To: "Poul-Henning Kamp" <phk@critter.freebsd.dk>, "Wolfgang Helbig" <helbig@Informatik.BA-Stuttgart.DE> Cc: "Blaz Zupan" <blaz@gold.amis.net>, freebsd-isdn@FreeBSD.ORG Subject: Re: i4b-L1-F_ill:What is this? (fwd) Message-ID: <1595423.3100873467@stefan.promo.de>
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--On Sam, 4. Apr 1998 20:30 Uhr +0200 "Poul-Henning Kamp" <phk@critter.freebsd.dk> wrote: > >>So we learned that the ASCOM-NT does not like an activation of layer1, >>if the activated layer1 is not used for anything. This is very similar >>to my NT from the german telecom. But then i4b tries to reactivate >>layer 1. This is successfull with my NT but seemingly not with the >>ASCOM-NT. > > I think this is related to the "the-phone-must-work-in-an-emegency- > phantom-power". Depending on your telco and the phase of the moon, > the NT will aggressively try to shut down everybody on the bus who > might be using power, to reduce the load on the telcos power bill. > > I belive the danish version of the Siemens NT act differently in > this respect if you don't plug in the powercord to the NT. As far as I have learned, the "emergency power" feature works like this: if the NT has local power (from its power cord), it supplies power to the bus, and, depending on the model, also drives it's U interface circuits from that. If there is no local power, the NT will power itself from the U interface, and will supply power to the S interface, but with polarity reversed. Only a single device on the bus is allowed to run with this setting; usually, you will have a switch on your phone to set whether to run in "emergency mode". Power consumption on the bus is severely limited (not so much because of the telcos power bill, but due to the max. line length of 6 km or so for the U interface, and the physical inability of providing a high current DC supply over that length of wire). Also I believe that the NT might not be involved at all in L1 transitions, but will simply relay U transitions to the S bus, so it might well be the switch thats responsible. This makes sense, as only the switch is involved in L2 states (and TEI assignment), so effectivly, the switch is conserving its ressources when deactiving L1 after some L2 idle time (because L1 must be brought up again before any L2 activity can take place). Just my 4 pf... Stefan -- Stefan Bethke Promo Datentechnik | Tel. +49-40-851744-18 + Systemberatung GmbH | Fax. +49-40-851744-44 Eduardstrasse 46-48 | e-mail: stefan@Promo.DE D-20257 Hamburg | http://www.Promo.DE/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isdn" in the body of the message
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